“Never before has there been anyone like you. You are something that never existed before and will never exist again. Isn’t that wonderful?”

Thus spoke director Frank Capra on “It’s a Wonderful Life,” which he considered the greatest of his own works. James Stewart also repeatedly called it his favorite among the roughly 80 films he made.

Fittingly then, Rotten Tomatoes dubs “IAWL,” “the holiday classic to define all holiday classics” — while the American Film Institute named it No. 1 on a 2006 list of the most inspiring movies ever made.

So this last of four December pieces on the film will try to pin down why it works so well; and we really must start with Capra, whose quote above points to the film’s message.

“There are just two things that are important,” the director insisted in a 1946 interview. “One is to strengthen the individual’s belief in himself, and the other, even more important right now, is to combat a modern trend toward atheism.”

Yes: In the most vivid and down-to-earth terms, “IAWL” shows that every person is vitally valuable; and moreover, that God is in control — even when everything seems to be falling apart.

Indeed, the film’s frame narrative facilitates this beautifully: By having angels review George Bailey’s tumultuous life, we are given a “heavenly perspective” — reminded that we don’t have “the big picture” on our own lives — that God takes a different view — that he is using even our failures and foibles in ways we don’t yet understand.

“IAWL” is based on a short story called “The Greatest Gift.” It was written by Philip Van Doren Stern and mailed to 200 of his friends as a Christmas card — after he was unable to find a publisher. (With the film’s popularity, however, it is now available in book form.) Stern based his tale on Dickens’ Christmas Carol — and so we can note how, like that classic work, his story involves a supernatural visitor providing the protagonist with a different perspective on his own life.

Yet both Stern and “IAWL” reverse Dickens: In the latter, a rotten man is shown how no one will miss him when he’s gone — whereas “Wonderful Life” takes a decent man and shows him exactly how much the world needs him.

Along the same lines, both tales involve a grouchy misanthrope (to which group we might add the Grinch); and both likewise revolve around a money-leading business that helps families afford homes (though Scrooge, of course, does it at exorbitant rates). As seen in so many other Christmas stories, there seems to be something archetypal about home and family at this time of year.

And speaking of reversal: Note also how the movie’s ending neatly flips the earlier bank-run: Nearly every single character who demanded money now arrives to give it back — reminding George that “no man is a failure who has friends.”

And in this way, George Bailey — who once wanted to leave Bedford Falls and see the world — comes to understand that home is more important than his own hopes and dreams. And thus, after humbling himself — first before Potter and then in a desperate prayer to God — George finally sets aside personal ambition once and for all; for he declares at last, “I don’t care what happens to me!”

Through his past actions, George has really already lived this out; but now he makes peace with it — grasping fully that family, friends, home and home-town are really what makes for a wonderful life.

And so, as he himself proclaims while stumbling up the street near the end: “Merry Christmas, movie house!”